[Bug c++/49118] New: Endless operator-> chain causes infinite loop

[potswa at mac dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49118

           Summary: Endless operator-> chain causes infinite loop
           Product: gcc
           Version: 4.5.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: potswa@mac.com


When the "drill-down" behavior is used to chain operator-> calls, a cycle in
the chain causes an immediate error message, but an endless acyclic chain
causes the compiler to hang, very slowly consuming memory.

Minimal case:

template< int n >
struct a { 
    a< n+1 > operator->() { return a< n+1 >(); }
};

int main() {
    a<0>()->x;
}

Suggested fix: If operator-> returns a template specialization, consider its
instantiation to be nested. This existing error message and limit-mechanism
would be appropriate:

error: template instantiation depth exceeds maximum of 500 (use
-ftemplate-depth-NN to increase the maximum) instantiating ‘struct a<500>’